The generation of energy by means of solar cells has up to now not yet reached the potential hoped for, since physical and technical problems prevented this. These are:
1. Qualitatively good solar cells are by far too expensive to produce in sufficient quantity to cover large areas therewith. PA1 2. The efficiency of known solar cells is low. Very good silicon solar cells today have an efficiency of 12 percent. GaAS solar cells reach up to 18 percent, but are much too expensive.
A summary of prior art and in particular a survey of present concentrator concepts and economics of concentration is included in: Proceedings of the Symposium on Films for solar Energy, published in: Journal of Vacuum Science and Technology, 12, Sept./Oct. 1975.